Magnet arrangement for a planar magnetron background and summary of the invention

ABSTRACT

A magnetic arrangement for a planar magnetron, in which an initial magnetic pole encompasses a second magnetic pole. This magnetic arrangement is moved linear in longitudinal direction to a target by a specific value and then moved back in opposite direction by the same value. In one version, an additional perpendicular motion is effected. The magnet arrangement is designed so that north and south pole interlock and waviform racetracks are generated. This enables constant sputtering from the entire target surface.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims priority under 35 U.S.C. § 119 from EuropeanPatent Application No. 050 07 339 filed Apr. 5, 2005, incorporatedherein by reference in its entirety.

The invention relates to an arrangement of magnets.

In a sputter system, plasma is generated in a sputter chamber undervacuum. The plasma is understood to be a quasi-neutral many-particlesystem in the form of gaseous blends of free electrons and ions as wellas possible neutral particles, i.e. atoms, molecules or radicals.Positive ions of the plasma are attracted by the negative potential of acathode, which features a so-called target. The positive ions impingeupon this target and knock away small particles that subsequentlyprecipitate on a substrate. The knocking away of these particles isreferred to as “sputtering.” The plasma contains ionized gases, whichcan, for example, be inert gases such as argon, in the event of anon-reactive sputtering. In the event of a reactive sputtering, forexample, oxygen is either used by itself or in conjunction with an inertgas.

The ions required for the sputtering process are generated through thecollisions of gas atoms and electrons in a glow discharge andaccelerated into the target forming the cathode with the assistance ofan electric field.

In conventional DC and HF sputtering, only few secondary electrons,emitted on sputtering the target, contribute to the ionization of thesputter gas atoms.

To improve the sputter effect, magnets are utilized near the target.Their magnetic field keeps the plasma at the target. Through theinteraction of the magnetic and the electric fields the charge carriersin the plasma primarily no longer move parallel to the electric fieldbut also at right angles to it, which results in cycloid electrontrajectories. As the deflection radii of the electrons are much smallerthan those of the ions, due to their low mass, the electrons concentratebefore the target surface. Therefore, the probability that sputter gasatoms are ionized via collisions with electrons is much higher. As aresult of the E×B drift of the electrons—the electrons follow atrajectory referred to as racetrack—and the concentration of plasmabefore the target surface, the electrons no longer fly directly to thesubstrate. Heating of the substrate is therefore reduced.

The much heavier ions fall onto the target, which has the effect of anegative electrode or cathode and sputter this. Ionizations thereforelargely occur where the magnetic field vector is parallel to the targetsurface. The plasma is most dense here, as a result of which the targetis most strongly eroded at this point. The glow discharge plasma isvirtually enclosed by the magnetic field and the electron trajectoriesare extended by the fact that the electrons rotate around the magneticfield lines serving as axes, thereby increasing the rate at which gasatoms and electrons collide.

To coat larger areas, planar magnetrons are generally used. These,however, have a lower target utilization, e.g. of 40% or less.

As a result, rotating cylinder magnetrons, which achieve a targetutilization of 90% and more, have been used more frequently in recenttimes.

A disadvantage which both cylinder magnetrons, which are occasionallyalso referred to as pipe cathodes, and planar magnetrons feature is theirregular wear of the targets. Pipe cathodes are less sputtered on theedges where in fact a re-coating can occur. So-called racetracks form inthe planar magnetrons, i.e. trenches from erosion caused by thearrangement of the magnets in the magnetrons. These erosion trenches aredirectly generated by the colliding ionized gas particles. These hit thetarget, acting as a negative electrode or cathode and serving as asputter, in an irregular way. The plasma trajectory determined by themagnetic field—which correlates with the electron trajectories—or theracetrack, in particular delimits the target utilization of planarmagnetrons; when the target is fully eroded at a given point, it can nolonger be used, even if there is still sufficient material at otherpoints. Although even a cylinder magnetron has a plasma racetrack whenstationary, which corresponds with the configuration of the magnets, notrench-like depression is formed on the rotating target.

Apart from the tube-like racetrack erosion, the rectangular planarmagnetrons with straight racetracks additionally feature a so-calledcross corner effect, which also delimits utilization of the target.Cross corners are the diagonally opposite corners of a rectangularmagnetron. If the magnetic field in a terminal region of the magnetroncathode differs from the magnetic field in the central area, e.g. isweaker, the electrons drift faster in this terminal region than in themiddle, i.e. they quickly arrive in the cross corner area. This causeselectron congestion in this area, which results in a denser ionizationand subsequently in increased erosion of the target. (cf. Q. H. Fan, L.Q. Zhou and J. J. Gracio, A cross-corner effect in a rectangularsputtering magnetron. J. Phys. D: Appl. Phy. 36 (2003), 244-251).

A magnetron sputter system already exists in which double T-shapedmagnets of an initial polarity are surrounded by rectangular frameworkmagnets of a second polarity (U.S. Pat. No. 5,458,759). This makes useof the arrangement of the magnets to achieve a consistent as possiblewear of the target.

Another procedure is also based on the assumption that the arrangementof magnets causes the erosions on the target (DE 197 01 575 A1). In sodoing, it suggests the positioning of a substrate in a directionperpendicular to the lengthwise direction of the cathode, while themagnets of the cathode are arranged so that they form two closed loopsof a sputtering erosion surface area and can be moved perpendicular tothe lengthwise direction of the cathode.

Furthermore, a sputter system exists with magnets that are arranged in ameander-like fashion (EP 0 105 407, FIG. 5). This generates apre-determined plasma sputtering area in the form of a meanderingelectron trajectory, which guarantees a relatively constant wear of thetarget. With this sputter system, no relative movement of target andmagnet system occurs. As a result, a re-coating between the individualmeander loops can occur and the target—which is larger than thesubstrate—cannot be fully sputtered.

Another existing magnetron sputtering cathode features an internalmagnetic south pole with a central bar from which tongues extendoutwards at right angles in regular intervals (EP 0 242 826 B1=U.S. Pat.No. 4,826,584). Here the exterior magnetic north exists of a rectangularframework, from the lengthwise sides of which tongues extend inwards atright angles that are arranged so that they lie between two tongues eachof the magnetic south. This results in a meander-shaped magnetic fieldand thus a meander-shaped erosion zone. The tongues of the south poleare all parallel to each other. Once again, with this sputtering cathodethere is no relative movement between the target and the magneticsystem.

A magnet arrangement for a sputter system also exists in which amagnetic north framework surrounds a linear south pole (Patent Abstractsof Japan, Vol. 013, no. 169 (C-587) & JP 63317671 A, FIG. 8). Betweenthis north and south pole there are further north and south poles to theright and the left of the linear south pole, which, however are notconnected to this south pole.

Furthermore, a magnet arrangement for a sputter system exists in which alargely ring-shaped north pole surrounds a linear south pole and inwhich the end of the south pole has arms extending to the north pole(U.S. Pat. No. 5,182,003). These arms are, however, not offset againsteach other.

Finally, a magnet arrangement for a sputter system exists in which aninitial oval magnetic pole surrounds a second linear magnetic pole (U.S.Pat. No. 5,026,471). Neither of the two magnetic poles has armsextending from it.

The invention is based on the task of optimally utilizing large targetsby means of a suitable management of erosion trenches and to keep thetarget as free as possible of re-deposits.

This problem is solved according to the present invention.

The invention thus pertains to a magnet arrangement for a planarmagnetron in which an initial magnetic pole encompasses a secondmagnetic pole. This magnet arrangement is moved linear in lengthwisedirection to a target by a specific value, and then moved back in theopposite direction by the same value. In one version an additionalperpendicular movement is also effected. The magnet arrangement isdesigned so that the north and south poles interlock to form waviformracetracks. As a result, constant sputtering from the entire targetsurface can be effected.

The benefit achieved by the invention consists of the fact that largeand plane targets with only a single erosion trench can be coated sothat more than 50% of its surface is covered by the erosion trenches.Through the relative movement between the target and magnet system thisresults in a homogeneous erosion profile. Through the slightinterlocking of opposing magnetic pole elements sputtering is alsoeffected in the middle of the target.

If the invention is advantageously designed, even long, wide targetswith only a single racetrack or erosion track can be coated. As the twopoles of the magnet arrangement interlock slightly in the middle, it ispossible to achieve a high target utilization and a virtually completere-coating free target surface with only one linear movement. In sodoing, north and south pole are arranged relatively to each other sothat meander-like racetracks are achieved on the target. Two opposingmeanders are so close to one another that the target surface is evenlysputtered when executing a linear movement toward the target length. Theheight of lift is ± half a meander interval.

Embodiment examples of the invention are shown in the drawings and aresubsequently described in more detail.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partial representation of an initial magnet arrangement in aplanar magnetron.

FIG. 2 is a partial representation of a second magnet arrangement in aplanar magnetron.

FIG. 3 is a partial representation of a third magnet arrangement in aplanar magnetron.

FIG. 4 is a representation of a magnet arrangement together with atarget and a substrate.

DETAILED DESCRIPTION

FIG. 1 shows a partial representation of an initial magnet configuration1 in accordance with the invention, with which constant utilization of atarget is enabled. In so doing, movements in two different directionsare, however, required. On the one hand, the magnet system must be movedalong the length of the target and, on the other, an additional movementalong the target width is required, so that no re-coating is obtained.The magnet configuration 1 shown in FIG. 1 continues on the right side(not shown) in a reversed image. The magnetic south pole of the magnetconfiguration consists of a transverse bar 2, on which arms 3 to 8 arearranged parallel to each other and perpendicular to bar 2.

On the one end of bar 2, two additional arms 9, 10 of the magnetic southare provided for, the longitudinal axis of which is arranged at an angleα to the longitudinal axis of the perpendicular bar 2. The angle α isapprox. 60°. At the end of the right and not displayed side of bar 2there are also arms that extend diagonally and correspond with arms 9and 10, which are, however not extended to the left but the right. Thesearms on the right are arranged mirror symmetrically to arms 9 and 10.

The north pole of magnet configuration 1 is arranged around the southpole like a frame, while an upper and a lower frame segment 11 and 12 aswell as a left lateral frame segment 13 are discernible. The rightlateral frame segment, corresponding with segment 13 is not depicted. Inthe middle of the left frame segment 13 an arm 16 is provided for, whichis opposite to the left end of bar 2. Correspondingly, an arm isprovided for on the right side, which corresponds to arm 16.

Between the two arms 9, 3; 3, 4; 4, 5; 10, 6; 6, 7; 7, 8 of bar 2 aretongues 21 to 23, 14 and 24 to 26, 15, which are perpendicular to framesegment 11 or 12 and oriented inwards.

The north and south pole of magnet configuration 1 are connected at theback with a yoke plate 17, 18. Line 20 indicates the erosion trackgenerated on the back of a target, which is not shown in FIG. 1.

When static, i.e. when magnet configuration 1 and the target do not moverelative to each other, erosion track or racetrack 20 form a singlemeander. To optimally utilize the target, magnet yoke 17, 18 must bemoved along the target length with magnet configuration 1 to determinethe meanders. In addition, a movement along the target width is requiredso that no re-coating occurs in the middle of the target.

The arrangement of magnets 9, 10 and 16 serves to remove or reduce thecross corner effect. Following a longer straight segment of racetrack, across corner effect can occur following a subsequent curve. On astraight racetrack alone, no cross corner effect will arise. This effectonly occurs at two opposite sides of the target, where electrons comeacross a straight segment after a curve (cf. FIG. 7B in DE 197.01 575A1). The invention described here does not have a racetrack consistingof an extended straight segment, it is always curved. If one omitsmagnet arm 16 and positions magnets 9 and 10 in parallel with the othermagnets, the racetrack is briefly straight along the target width and across corner effect is to be expected.

FIG. 2 depicts a second magnet configuration 30 with which only onemovement along the target length is required. A movement along thetarget width is not required. In so doing, the movement of magnetconfiguration 30 is effected linear along the length of a target. At theend of a target, a return movement occurs.

One of the poles of magnet configuration 30, e.g. the south pole hasequidistant upper arms 31 to 35 and equidistant lower arms 36 to 40. Thelongitudinal axes of the lower arms 36 to 40 are parallel to thelongitudinal axes of the upper arms 31 to 35, however, they arelaterally offset so that they run through a point that marks the middlebetween the longitudinal axes of upper arms 31 to 35.

The ends of arms 31 to 35 or 36 to 40, that are inwards oriented end inrectangular blocks 41 to 45 and 46 to 50, which are connected toconnection elements 51 to 59 that create a connection between blocks 41to 45 and blocks 46 to 50. These connection elements 51 to 59 arearranged at an angle β to the longitudinal axes of arms 31 to 35 and 36to 40.

As a result, all components of the south pole are magneticallyconnected.

The other pole, e.g. the north pole of magnet configuration 30 is formedby several hood-like sub-magnets, which each encompass an arm 31 to 35or 36 to 40 of the south pole. These sub-magnets feature two sides 61,62 or 63, 64 or 65, 66 or 67, 68 or 69, 70 each that are arrangeddiagonally to the center axis of arms 31 to 35 and 36 to 40, the upperends of which are connected to each other by means of blocks 71 to 75,the longitudinal axes of which is horizontal. The lower ends of sides 61to 70 are also connected with blocks 125 to 130, which have verticallyoriented longitudinal axes. The lower sub-magnets are also arranged incorrespondence with the upper sub-magnets of the north pole described.The ends of sides 80 to 88 adjoin to blocks 90 to 94 and 100 to 104. Theformer blocks 90 to 94 are vertically oriented while the latter blocks100 to 104 are oriented horizontally.

The racetrack forming when static, i.e. without relative movementbetween magnet configuration 30 and the target, is designated as 105 andforms two superimposed wave curves similar to a sinus curve.

FIG. 2 not only shows the north and south poles but also the position ofthe zero-crossing of the perpendicular component of the magnetic fieldon the target surface. The direction in which magnet configuration 30 ismoved relative to a target is indicated by a double arrow 111. Thisarrow shows that the movement is only effected in the longitudinaldirection of the target, namely once to the right and subsequently tothe left, etc. In so doing, the stroke length is ± half a meanderinterval. In this case the meander interval is considered to be theinterval between two peaks of a sinus-like wave 105. The size of doublearrow 111 corresponds approximately with the meander interval.

The information on the y-axis and x-axis are provided in mm, which areof no relevance to the invention. They merely indicate the spatial sizeof a realisable magnet arrangement.

As a result of the design of magnet configuration 30, which isasymmetrical to the center axis, sputtering is also effected in thecenter area; however, re-coating is effected between the loops. It isonly through the movement of the magnetic field along the target lengththat a re-coating free target surface occurs, with the exception of theedges of the target.

With magnet configuration 30, a re-coating area arises at the top andbottom of the target. This re-coating area is not desired and can bereduced, e.g. through targets in the form of a parallelogram. However,it can also be reduced by positioning the meanders at an angle.

Magnet configuration 120, in which the meanders are positioned at anangle, is depicted in FIG. 3. As the number of magnetic elements andtheir basic arrangement is the same as the one in FIG. 2, these magneticelements have the same designations as in FIG. 2. In this case, arms 31to 40 are inclined by an angle γ to the perpendicular. This results intwo sinus-like wave curves arranged on top of each other, as racetrack121. Through the inclination of the meanders it is possible to reducere-coating at the two ends of the target.

Magnet configuration 120 of FIG. 3 is moved relative to the target inthe same manner as magnet configuration 30 of FIG. 2.

FIG. 4 schematically depicts an arrangement, which not only comprisesmagnet configuration 1 but also a target 77 and a substrate 78. Themagnet configuration is the same as in FIG. 1, which is why theindividual magnet elements feature the same designations.

Target 77 and substrate 78 are solidly arranged in a sputter chamber notdepicted. However, below target 77, magnet configuration 1 with yoke 17,18, can be moved towards the arrows 97, 98. A carrier plate 113connected to a drive not depicted, is provided for this purpose, theends of which are guided by tracks 114, 115. A slide 116 is arranged onthis carrier plate 113, which carries magnet configuration 1 via apillar 117. As the slide 116 can be moved towards arrow 98, the magnetconfiguration 1 can be moved relative to target 77, as required.

With the above embodiment examples of the invention the targets arelonger than the magnet construction as the magnets are moved along thetarget length. The target width, however, is smaller than the width ofthe magnet arrangement. The size of the target is determined by the sizeand form of the racetrack and the movement.

1-25. (canceled)
 26. A magnet arrangement for a planar magnetron, inwhich an initial magnetic pole encompasses a second magnetic pole andthe second magnetic pole has a first group of arms which are oriented inan initial direction, as well as a second group of arms which areoriented in a direction opposite to the initial direction, wherein thelongitudinal axis of the first group of arms is offset against thelongitudinal axis of the second group of arms so that the longitudinalaxis of an arm of the first group is located between the longitudinalaxes of two arms of the second group.
 27. The magnet arrangement ofclaim 26, wherein the arms of the first group are arrangedequidistantly.
 28. The magnet arrangement of claim 26, wherein the armsof the second group are arranged equidistantly.
 29. The magnetarrangement of claim 26, wherein the first group of arms and the secondgroup of arms are connected via diagonal bars.
 30. The magnetarrangement of claim 29, wherein the diagonal bars are connected viablocks with the arms.
 31. The magnet arrangement of claim 26, whereinthe initial pole features a first group of diagonal arms of which twoeach form a gable roof-like element, in which one the end of an arm isin contact with a first block and the other end of the arm with a secondblock.
 32. The magnet arrangement of claim 31, wherein the longitudinalaxis of the first block is perpendicular to the longitudinal axis of thesecond block.
 33. The magnet arrangement of claim 31, wherein a gableroof-like element of the first pole encompasses an arm of the secondpole.
 34. The magnet arrangement of claim 31, wherein the two diagonalarms of a gable roof-like element are mirror symmetrical to each other.35. The magnet arrangement of claim 31, wherein the two diagonal arms ofa gable roof-like element have different angles of inclination to alongitudinal axis through a block.
 36. The magnet arrangement of claim26, wherein the arms of the second magnetic pole have different anglesof inclination to a longitudinal axis through a block of the firstmagnetic pole.
 37. The magnet arrangement of claim 26, wherein themagnetic arrangement can be moved forwards and backwards.
 38. The magnetarrangement of claim 26, wherein the magnetic arrangement can be movedin x direction and relative to a target.
 39. The magnet arrangement ofclaim 38, wherein the magnetic arrangement can be moved forwards andbackwards.
 40. The magnet arrangement of claim 26, wherein the magneticarrangement is part of the magnetron of a sputter system.
 41. The magnetarrangement of clam 26, wherein the magnetic arrangement can be movedrelative to a target.
 42. The magnet arrangement of claim 40, whereinthe magnetic arrangement is located near a target.
 43. The magnetarrangement of claim 42, wherein the target lies opposite a substrate.44. The magnet arrangement of claim 41, wherein the magnetic arrangementcan be moved in x or y direction, relative to the target.